December 20, 2014Open Access
Comparing GFR Estimating Equations Using Cystatin C and Creatinine in Elderly Individuals
Key Result
The CKD-EPI equations were superior or similar to Japanese, BIS, and CAPA equations in elderly adults, with the combined eGFRcr-cys performing better than eGFRcr or eGFRcys alone.
Study Design
Type
Observational (n=805)
Structured PICO
Does the use of Japanese, BIS, or CAPA equations, or the combination of creatinine and cystatin C, improve GFR estimation accuracy compared to CKD-EPI equations in elderly individuals?
P
Population
805 community-dwelling elderly adults (mean age 80.3 years) from the AGES-Reykjavik Study evaluated for the accuracy of GFR estimating equations.
E
Exposure
GFR estimation using Japanese, Berlin Initiative Study (BIS), and Caucasian and Asian pediatric and adult subjects (CAPA) equations, as well as the combination of creatinine and cystatin C (eGFRcr-cys).
C
Comparator
Measured GFR (mGFR) using plasma clearance of iohexol (reference standard), and eGFR using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.
O
Outcome
Equation performance evaluated using bias, precision, and two measures of accuracy.surrogate
In community-dwelling elderly individuals, the CKD-EPI equations remain the preferred method for estimating GFR, with the combination of creatinine and cystatin C providing the best accuracy.
Abstract
Current guidelines recommend reporting eGFR using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations unless other equations are more accurate, and recommend the combination of creatinine and cystatin C (eGFRcr-cys) as more accurate than either eGFRcr or eGFRcys alone. However, preferred equations and filtration markers in elderly individuals are debated. In 805 adults enrolled in the community-based Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study, we measured GFR (mGFR) using plasma clearance of iohexol, standardized creatinine and cystatin C, and eGFR using the CKD-EPI, Japanese, Berlin Initiative Study (BIS), and Caucasian and Asian pediatric and adult subjects (CAPA) equations. We evaluated equation performance using bias, precision, and two measures of accuracy. We first compared the Japanese, BIS, and CAPA equations with the CKD-EPI equations to determine the preferred equations, and then compared eGFRcr and eGFRcys with eGFRcr-cys using the preferred equations. Mean (SD) age was 80.3 (4.0) years. Median (25th, 75th) mGFR was 64 (52, 73) ml/min per 1.73 m(2), and the prevalence of decreased GFR was 39% (95% confidence interval, 35.8 to 42.5). Among 24 comparisons with the other equations, CKD-EPI equations performed better in 9, similar in 13, and worse in 2. Using the CKD-EPI equations, eGFRcr-cys performed better than eGFRcr in four metrics, better than eGFRcys in two metrics, and similar to eGFRcys in two metrics. In conclusion, neither the Japanese, BIS, nor CAPA equations were superior to the CKD-EPI equations in this cohort of community-dwelling elderly individuals. Using the CKD-EPI equations, eGFRcr-cys performed better than eGFRcr or eGFRcys.